A basic teleconferencing system typically includes at each respective site a camera for capturing a view of the participants at that site and a display for displaying a view of the participants at the other site. In traditional high end teleconferencing designs, multiple cameras are used for capturing images of participants at a site, with no (or minimal) overlap and multiple displays at another site display these different captured images. In either of these types of configurations, each display shows the image of the remote participants with a perspective that is determined by the position of the camera, which is coupled to that display. In some cases, a single camera is centrally positioned over the display device(s), and captures a wide field of view of the site. In this configuration, the perspective of the remote participants is only correct for a centrally located viewer, and only as to the remote participant seated directly in line with the camera axis. For viewers who are located to either side of the display system, the images of the remote participants do not have the correct perspective, since these viewers would normally see the remote participants from the side if in fact they were seated across from each other in the same conference room. Similarly, as to the remote participants who are located off to the side of the camera axis, their images do not have the correct perspective either.
In an attempt to obtain the proper perspective and eye contact for multiple participants, multiple cameras are typically used, with each camera focused on a particular viewing location or participant. The image stream from each camera is then provided to a corresponding display device. In this fashion, the displays show each remote participant “head on”. However, this solution is also not entirely correct since the “head on” display of each remote participant also does not provide the correct perspective based on each particular perspective of the remote participants.
One approach for a multiple participant videoconferencing systems is described by Nakazawa, et al. al., in Proposal for a New Eye Contact Method for Teleconference, IEICE Transactions on Communications, vol. E76-B, no. 6, pp. 618-625, June 1993. Nakazawa describes a teleconferencing system for two local and two remote participants in which each site has two cameras, two projectors, and a single double-lenticular screen at each site. FIG. 1 illustrates Nakazawa's system, in which participants A and B are at one site, and participants C and D are at the other remote site. Participant A observes the images taken by camera A′ and rear-screen projected by projector A″ on the double lenticular screen. The complementary situation applies to participants B, C and D.
There are a number of problems with Nakazawa's system. First, as is clearly seen in FIG. 1, the position of each camera does not properly capture the perspective of the local participant as if he was located at the virtual location corresponding to the camera position and establishing eye contact with a remote participant. It can be seen that each of the cameras is angled somewhat inwardly to capture a field of view of both participants. Thus, camera A′ has a very wide field of view, and is angled to the left of participant C so as to capture an image stream of both C and D even though they are different seating positions. Camera B′ is likewise angled to the right of participant D so as to capture an image stream of both C and D. However, if participant A were indeed located at the virtual position Av shown in FIG. 1, he would be located directly across from, and look directly at, participant C to establish eye contact, instead of at the angle of camera A′ as shown. Likewise, participant A would turn significantly to the left to establish eye contact with participant D, also at a much different angle than that shown for camera A′. As a result, participant A does not in fact see the images of participants C and D on his screen with the correct perspective for proper eye to eye contact.
A second problem with Nakazawa's system is that the design does not readily scale beyond the two-by-two configuration described. Nakazawa states that in this design there are as many cameras and projectors as there are participants, but then admits that this approach is not realistic for implementation, and suggests that one camera and one projector be shared by multiple persons. However, by definition, a single camera cannot correctly capture the proper perspective for eye-to-eye contact with between one participant (represented by the camera) and multiple remote participants.
Accordingly, it is desirable to provide a videoconferencing system that can display the images of multiple participants at a remote site with both the proper visual perspective of each displayed position of another site as if her position were located at the other site, and with the appropriate eye-to-eye contact.